<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box{
            width: 400px;
            height: 500px;
            background-color: green;
            /* transition: width 3s,background-color 5s; */
            transition: all 1s;
        }
        .box:hover{
            width: 500px;
            background-color: red;

        }
    </style>
</head>
<body>
    <div class="box"></div>
</body>
</html>